Heat sink



FIG. 1 represents a perspective view of a heat sink showing my newdesign;

FIG. 2 represents a side view thereof;

FIG. 3 represents a side view of one part of the heat sink shown inFIGS. 1 and 2 for ease of illustration; and,

FIG. 4 represents a perspective view of the heat sink part shown in FIG.3.

The ornamental design for a heat sink, as shown and described.